Flame resistant polyester compositions, method of manufacture, and articles thereof

ABSTRACT

A thermoplastic polyester composition comprising, based on the total weight of the composition, a chlorine- and bromine-free combination of: from 40 to 60 wt % of a polyester; from 25 to 35 wt % of a reinforcing filler; from 2 to 8 wt % of a flame retardant synergist selected from the group consisting of melamine polyphosphate, melamine cyanurate, melamine pyrophosphate, melamine phosphate, and combinations thereof; from 5 to 15 wt % of a phosphinate salt flame retardant; from more than 0 to less than 5 wt % of an impact modifier component comprising a poly(ether-ester) elastomer and a (meth)acrylate impact modifier; from more than 0 to 5 wt % poly(tetrafluoroethylene) encapsulated by a styrene-acrylonitrile copolymer; from more than 0 to 2 wt % of a stabilizer; wherein the thermoplastic polyester composition contains less than 5 wt % of a polyetherimide.

BACKGROUND

This disclosure relates to polyester compositions, method of manufactureof the compositions, and articles thereof.

Thermoplastic polyester compositions, such as poly(alkyleneterephthalates), have valuable characteristics including strength,toughness, high gloss, and solvent resistance. Polyesters therefore haveutility as materials for a wide range of applications, from automotiveparts to electric and electronic appliances. Because of their wide use,particularly in electronic applications, it is desirable to provideflame retardancy to polyesters.

Numerous flame retardants (FR) for polyesters are known, but manycontain halogens, usually chlorine and/or bromine. Halogenated flameretardant agents are less desirable because of the increasing demand forecologically friendly ingredients. Halogen-free flame-retardants, suchas phosphorus- and nitrogen-based compounds can be used as well.Unfortunately, it can be difficult to achieve excellent flame retardancyin very thin sections.

More ecologically compatible flame retardant (eco-FR) formulations basedon aluminum salts of phosphinic or diphosphinic acid compounds andmelamine compounds have been developed to overcome environmental issuesof halogenated flame retardants. However, these eco-FR compositions canhave reduced impact strength and tensile strength, as well as lessdesirable flow properties compared to compositions having halogenatedflame retardants. The addition of small amounts of a polyetherimide(PEI), in particular ULTEM 1010 from Sabic Innovative Plastics, hasboosted the mechanical properties of the eco-FR compositions. However,in some circumstances PEI lowers the comparative tracking index (CTI)compared to halogenated frame retardants, i.e., the presence of PEI canincrease the tendency to form conductive leakage paths on the surface ofa molded article.

Thus, there remains a need for eco-FR thermoplastic polyestercompositions having good flame retardant properties and comparable orimproved mechanical properties, including ductility, flexural strength,CTI, and stiffness relative to compositions comprising halogenated flameretardants and eco-FR compositions comprising PEI.

BRIEF SUMMARY OF THE INVENTION

Disclosed herein is a thermoplastic polyester composition comprising,based on the total weight of the composition, a chlorine- andbromine-free combination of: (a) from 40 to 60 wt % of a polyester; (b)from 25 to 35 wt % of a reinforcing filler, (c) from 2 to 8 wt % of aflame retardant synergist selected from the group consisting of melaminepolyphosphate, melamine cyanurate, melamine pyrophosphate, melaminephosphate, and combinations thereof; (d) from 5 to 15 wt % of aphosphorous flame retardant comprising: a phosphinate of formula (I)[(R¹)(R²)(PO)—O]⁻ _(n)M^(m+)  (I),a diphosphinate of formula (II)[(O—POR¹)(R³)(POR²—O)]²⁻ _(n)M^(m+) _(x)  (II), and/ora polymer derived from the phosphinate of formula (I) or thediphosphinate of the formula (II), wherein R¹ and R² are eachindependently the same or different, and are H, linear or branched C₁-C₆alkyl, or C₆-C₁₀ aryl; R³ is C₁-C₁₀, linear or branched alkylene, C₆-C₁₀arylene, C₇-C₁₁ alkylarylene, or C₇-C₁₁ arylalkylene; M is an alkalineearth metal, alkali metal, Al, Ti, Zn, Fe, or B; m is 1, 2, 3 or 4; n is1, 2, or 3; and x is 1 or 2; (e) from more than 0 to less than 5 wt % ofan impact modifier component comprising a poly(ether-ester) elastomerand a (meth)acrylate impact modifier, (f) from more than 0 to 5 wt %poly(tetrafluoroethylene) encapsulated by a styrene-acrylonitrilecopolymer; (g) from more than 0 to 2 wt % of a stabilizer, wherein thethermoplastic polyester composition contains less than 5 wt % of apolyetherimide.

Also disclosed is a thermoplastic polyester composition comprising,based on the weight of the composition, a chlorine- and bromine-freecombination of: (a) from 40 to 60 wt % of polybutylene terephthalate,(b) from 25 to 35 wt % of a glass fiber filler, (c) from 2 to 8 wt % ofa flame retardant synergist selected from the group consisting ofmelamine polyphosphate, melamine cyanurate, melamine pyrophosphate,melamine phosphate, and combinations thereof; (d) from more than 10 to15 wt % a phosphinate of formula (I)[(R¹)(R²)(PO)—O]⁻ _(m)M^(m+)  (I),a diphosphinate of formula (II)[(O—POR¹)(R³)(POR²—O)]²⁻ _(n)M^(m+) _(x)  (II),and/or a polymer derived from the phosphinate of formula (I) or thediphosphinate of the formula (II), wherein R¹ and R² are identical ordifferent and are H, linear or branched C₁-C₆ alkyl, or C₆-C₁₀ aryl; R³is C₁-C₁₀, linear or branched alkylene, C₆-C₁₀ arylene, C₇-C₁₁alkylarylene, or C₇-C₁₁ arylalkylene; M is an alkaline earth metal,alkali metal, Al, Ti, Zn, Fe, or B; m is 1, 2, 3 or 4; n is 1, 2, or 3;and x is 1 or 2; (e) at least 1% to less than 5 weight % of impactmodifier component comprising a combination of (i) a poly(ether-ester)elastomer and (ii) a core-shell (meth)acrylate impact modifier; whereinthe poly(ether-ester) elastomer comprises long-chain ester units offormula (III):-GOCOR′COO—  (III);and short-chain ester units having units of formula (IV):-DOCOR′COO—  (IV),wherein R′ is a divalent aromatic radical remaining after removal ofcarboxyl groups from terephthalic acid, isophthalic acid, or acombination of terephthalic acid and isophthalic acid; G is a divalentpolyalkylene oxide radical remaining after removal of terminal hydroxylgroups from a poly(alkylene oxide) glycol having a number-averagemolecular weight of 100 to 2500; and D is a divalent alkylene radicalremaining after removal of hydroxyl groups from aliphatic diols having amolecular weight from 62 to 286; and wherein the core-shellmeth(acrylate) impact modifier has a crosslinked poly(butyl acrylate)core with a grafted poly(methyl methacrylate) shell; (f) from more than0 to 5 wt % poly(tetrafluoroethylene) encapsulated by astyrene-acrylonitrile copolymer; and (g) from more than 0 wt % to 2 wt %of a stabilizer; wherein the halogen free composition contains less than5 wt % of a polyetherimide; and wherein an article molded from thecomposition exhibits (a) a flexural modulus that is more than 9800 MPa,(b) a flexural stress that is more than 150 MPa, (c) an unnotched impactstrength that is more than 470 Joules/meter, and (d) a V0 rating at 0.8mm, measured in accordance with UL 94.

Still further disclosed is a thermoplastic polyester compositioncomprising, based on the weight of the composition, a halogen-freecombination of: (a) from 40 to 60 wt % of polybutylene terephthalate;(b) from 25 to 35 wt % glass fiber filler, (c) from 2 to 8 wt % of aflame retardant synergist selected from the group consisting of melaminepolyphosphate, melamine cyanurate, melamine pyrophosphate, melaminephosphate, and combinations thereof; (d) from more than 10 to 15 wt % aphosphinate of formula (I)[(R¹)(R²)(PO)—O]⁻ _(m)M^(m+)  (I),a diphosphinate of formula (II)[(O—POR¹)(R³)(POR²—O)]²⁻ _(n)M^(m+) _(x)  (II),and/or a polymer derived from the phosphinate of formula (I) or thediphosphinate of the formula (II), wherein R¹ and R² are identical ordifferent and are H, or linear or branched C₁-C₆ alkyl; R³ is C₁-C₁₀,linear or branched alkylene; M is aluminum; m is 3; n is 3; and x is 1or 2; (e) at least 1 to less than 5 wt % of impact modifier componentcomprising a combination of (i) a poly(butyleneterephthalate-polytetrahydrofuran) block copolymer and (ii) a core-shell(meth)acrylate impact modifier having a crosslinked poly(butyl acrylate)core with a grafted poly(methyl methacrylate) shell; (f) from more than0 to 5 wt % poly(tetrafluoroethylene) encapsulated by astyrene-acrylonitrile copolymer; and (g) from more than 0 wt % to 2 wt %of a stabilizer; wherein the halogen free composition contains less than2 wt % of a polyetherimide; and wherein an article molded from thecomposition exhibits (a) a flexural modulus that is more than 9800 MPa,(b) a flexural stress is more than 150 MPa, (c) an unnotched impactstrength that is more than 470 Joules/meter, and (d) a V0 rating at 0.8mm, measured in accordance with UL 94.

Also disclosed are methods for the manufacture of the foregoingcompositions; and articles comprising the foregoing compositions.

DETAILED DESCRIPTION OF THE INVENTION

Our invention is based on the discovery that that it is possible to makea glass filled halogen free flame retarding composition that exhibitsmany useful properties: namely, good flame retardancy performance (i.e.V0 at 0.80 mm), higher CTI performance, improved impact properties andimproved flexural properties by the use of a specific combination ofelastomers, as compared to a composition that does not use thecombination of elastomers. Described herein is a flame retardantthermoplastic polyester composition that is chlorine- and bromine-free,and that includes a polyester, a reinforcing filler, a melamine-basedflame retardant synergist, a phosphinate salt flame retardant, ananti-drip agent, an impact modifier component comprising apoly(ether-ester) elastomer and an acrylate impact modifier, astabilizer, and only optionally a polyetherimide. Use of the specificcomponents in the amounts disclosed herein allows manufacture of achlorine- and bromine-free composition with excellent flame retardanceand improved flow and CTI, while maintaining and the desirablemechanical properties of currently used glass-filled eco-FRformulations, even in the absence of a polyetherimide. In particular,the compositions can have very useful impact strength properties,flexural properties, heat stability, flow properties, and/or highresistance against electrical breakdown.

As used herein the singular forms “a,” “an,” and “the” include pluralreferents. The term “combination” is inclusive of blends, mixtures,alloys, reaction products, and the like. Unless defined otherwise,technical and scientific terms used herein have the same meaning as iscommonly understood by one of skill. Compounds are described usingstandard nomenclature. The term “and a combination thereof” is inclusiveof the named component and/or other components not specifically namedthat have essentially the same function.

Other than in the operating examples or where otherwise indicated, allnumbers or expressions referring to quantities of ingredients, reactionconditions, and the like, used in the specification and claims are to beunderstood as modified in all instances by the term “about.” Variousnumerical ranges are disclosed in this patent application. Because theseranges are continuous, they include every value between the minimum andmaximum values. The endpoints of all ranges reciting the samecharacteristic or component are independently combinable and inclusiveof the recited endpoint. Unless expressly indicated otherwise, thevarious numerical ranges specified in this application areapproximations. The term “from more than 0 to” an amount means that thenamed component is present in some amount more than 0, and up to andincluding the higher named amount.

All ASTM tests and data are from the 2003 edition of the Annual Book ofASTM Standards unless otherwise indicated. All cited references areincorporated herein by reference.

For the sake of clarity, the terms “terephthalic acid group,”“isophthalic acid group,” “butanediol group,” and “ethylene glycolgroup” have the following meanings. The term “terephthalic acid group”in a composition refers to a divalent 1,4-benzene radical (-1,4-(C₆H₄)—)remaining after removal of the carboxylic groups from terephthalicacid-. The term “isophthalic acid group” refers to a divalent1,3-benzene radical (-(-1,3-C₆H₄)—) remaining after removal of thecarboxylic groups from isophthalic acid. The “butanediol group” refersto a divalent butylene radical (—(C₄H₈)—) remaining after removal ofhydroxyl groups from butanediol. The term “ethylene glycol group” refersto a divalent ethylene radical (—(C₂H₄)—) remaining after removal ofhydroxyl groups from ethylene glycol. With respect to the terms“terephthalic acid group,” “isophthalic acid group,” “ethylene glycolgroup,” “butane diol group,” and “diethylene glycol group” being used inother contexts, e.g., to indicate the weight % of the group in acomposition, the term “isophthalic acid group(s)” means the group havingthe formula (—O(CO)C₆H₄(CO)—), the term “terephthalic acid group” meansthe group having the formula (—O(CO)C₆H₄(CO)—), the term diethyleneglycol group means the group having the formula (—O(C₂H₄)O(C₂H₄)—), theterm “butanediol group” means the group having the formula (—O(C₄H₈)—),and the term “ethylene glycol groups” means the group having formula(—O(C₂H₄)—).

Polyesters for use in the present thermoplastic compositions havingrepeating structural units of formula (I)

wherein each T is independently the same or different divalent C₆₋₁₀aromatic group derived from a dicarboxylic acid or a chemical equivalentthereof, and each D is independently a divalent C₂₋₄ alkylene groupderived from a dihydroxy compound or a chemical equivalent thereof.Copolyesters containing a combination of different T and/or D groups canbe used. Chemical equivalents of diacids include the correspondingesters, alkyl esters, e.g., C₁₋₃ dialkyl esters, diaryl esters,anhydrides, salts, acid chlorides, acid bromides, and the like. Chemicalequivalents of dihydroxy compounds include the corresponding esters,such as C₁₋₃ dialkyl esters, diaryl esters, and the like. The polyesterscan be branched or linear. Exemplary polyesters include poly(alkyleneterephthalate) (“PAT”), poly(1,4-butylene terephthalate), (“PBT”),poly(ethylene terephthalate) (“PET”), poly(ethylene naphthalate)(“PEN”), poly(butylene naphthalate), (“PBN”), poly(propyleneterephthalate) (“PPT”), poly(cyclohexane dimethanol terephthalate)(“PCT”), poly(cyclohexane-1,4-dimethylene cyclohexane-1,4-dicarboxylate)also known as poly(1,4-cyclohexanedimethanol 1,4-dicarboxylate)(“PCCD”), poly(cyclohexanedimethanol terephthalate),poly(cyclohexylenedimethylene-co-ethylene terephthalate),cyclohexanedimethanol-terephthalic acid-isophthalic acid copolymers andcyclohexanedimethanol-terephthalic acid-ethylene glycol (“PCTG” or“PETG”) copolymers. When the molar proportion of cyclohexanedimethanolis higher than that of ethylene glycol the polyester is termed PCTG.When the molar proportion of ethylene glycol is higher than that ofcyclohexane dimethanol the polyester is termed PETG.

The polyesters can be obtained by methods well known to those skilled inthe art, including, for example, interfacial polymerization,melt-process condensation, solution phase condensation, andtransesterification polymerization. Such polyester resins are typicallyobtained through the condensation or ester interchange polymerization ofthe diol or diol equivalent component with the diacid or diacid chemicalequivalent component. Methods for making polyesters and the use ofpolyesters in thermoplastic molding compositions are known in the art.Conventional polycondensation procedures are described in the following,see, generally, U.S. Pat. Nos. 2,465,319, 5,367,011 and 5,411,999. Thecondensation reaction can be facilitated by the use of a catalyst, withthe choice of catalyst being determined by the nature of the reactants.The various catalysts are known in the art. For example, a dialkyl estersuch as dimethyl terephthalate can be transesterified with butyleneglycol using acid catalysis, to generate poly(butylene terephthalate).It is possible to use a branched polyester in which a branching agent,for example, a glycol having three or more hydroxyl groups or atrifunctional or multifunctional carboxylic acid has been incorporated.

Commercial examples of PBT include those available under the trade namesVALOX 315 and VALOX 195, manufactured by SABIC Innovative Plastics.

A combination of polyesters can be used, for example a combination ofvirgin polyesters (polyesters derived from monomers rather than recycledpolymer, including virgin poly(1,4-butylene terephthalate). Alsocontemplated herein are second polyesters comprising minor amounts,e.g., 0.5 to 30 wt %, of units derived from aliphatic acids and/oraliphatic polyols to form copolyesters. The aliphatic polyols includeglycols, such as poly(ethylene glycol). Such polyesters can be madefollowing the teachings of, for example, U.S. Pat. No. 2,465,319 toWhinfield et al., and U.S. Pat. No. 3,047,539 to Pengilly. Secondpolyesters comprising block copolyester resin components are alsocontemplated, and can be prepared by the transesterification of (a)straight or branched chain poly(alkylene terephthalate) and (b) acopolyester of a linear aliphatic dicarboxylic acid and, optionally, anaromatic dibasic acid such as terephthalic or isophthalic acid with oneor more straight or branched chain dihydric aliphatic glycols.Especially useful when high melt strength is important are branched highmelt viscosity resins, which include a small amount of, e.g., up to 5mole percent based on the acid units of a branching component containingat least three ester forming groups. The branching component can be onethat provides branching in the acid unit portion of the polyester, inthe glycol unit portion, or it can be a hybrid branching agent thatincludes both acid and alcohol functionality. Illustrative of suchbranching components are tricarboxylic acids, such as trimesic acid, andlower alkyl esters thereof, and the like; tetracarboxylic acids, such aspyromellitic acid, and lower alkyl esters thereof, and the like; orpreferably, polyols, and especially preferably, tetrols, such aspentaerythritol; triols, such as trimethylolpropane; dihydroxycarboxylic acids; and hydroxydicarboxylic acids and derivatives, such asdimethyl hydroxyterephthalate, and the like. Branched poly(alkyleneterephthalate) resins and their preparation are described, for example,in U.S. Pat. No. 3,953,404 to Borman. In addition to terephthalic acidunits, small amounts, e.g., from 0.5 to 15 mole percent of otheraromatic dicarboxylic acids, such as isophthalic acid or naphthalenedicarboxylic acid, or aliphatic dicarboxylic acids, such as adipic acid,can also be present, as well as a minor amount of diol component otherthan that derived from 1,4-butanediol, such as ethylene glycol orcyclohexane dimethanol, etc., as well as minor amounts of trifunctional,or higher, branching components, e.g., pentaerythritol, trimethyltrimesate, and the like.

In an embodiment, a PBT is used in combination with a poly(ethyleneterephthalate), poly(1,4-butylene terephthalate), poly(ethylenenaphthalate), poly(1,4-butylene naphthalate), poly(trimethyleneterephthalate), poly(1,4-cyclohexanenedimethylene1,4-cyclohexanedicarboxylate), poly(1,4-cyclohexanedimethyleneterephthalate), poly(1,4-butylene-co-1,4-but-2-ene diol terephthalate),poly(cyclohexanedimethylene-co-ethylene terephthalate), or a combinationthereof. The weight ratio of PBT:other polyester can vary from 50:50 to99:1, specifically from 80:20 to 99:1.

Any of the foregoing first and optional second polyesters can have anintrinsic viscosity of 0.4 to 2.0 deciliters per gram (dL/g), measuredin a 60:40 by weight phenol/1,1,2,2-tetrachloroethane mixture at 23° C.The PBT can have a weight average molecular weight of 10,000 to 200,000Daltons, specifically 50,000 to 150,000 Daltons as measured by gelpermeation chromatography (GPC). The polyester component can alsocomprise a mixture of different batches of PBT prepared under differentprocess conditions in order to achieve different intrinsic viscositiesand/or weight average molecular weights. In an embodiment, a combinationof polyesters having different viscosities is used, for example acombination comprising a first polyester having a viscosity from 0.5 to1.0 dL/g and a second polyester having an intrinsic viscosity rangingfrom 1.1 to 1.4 dL/g. One or both of the polyesters can be a PBT. Theweight ratio of the two polyesters of different viscosity can beadjusted to achieve the desired properties, and is generally within therange of 20:80 to 80:20, more specifically from 40:60 to 60:40.

The amount of the polyester in the compositions can be adjusted toprovide the desired properties within the limits described herein, whichvaries with the specific application. The composition can accordinglycomprise from 40 to 60 wt %, specifically from 45 to 55 wt %, of thepolyester, wherein each of the foregoing is based on the total weight ofthe composition.

The composition includes a melamine flame retardant synergist and aphosphinate flame retardant. It has been found that this combinationprovides excellent flame retardance, in combination with advantageousphysical properties in the absence of PEI. The flame retardant synergistis melamine pyrophosphate, melamine polyphosphate, melamine phosphate,or melamine cyanurate. Combinations comprising the foregoing can beused.

The flame retardant synergist is present in the composition in an amountfrom 2 to 8 wt %, specifically from 3 to 7 wt %, still more specificallyfrom 4 to 6 wt %, each based on the total weight of the composition.

The flame retardant synergist is used in combination with one or morephosphinic acid salts. The phosphinates and diphosphinates include thoseset forth in U.S. Pat. No. 6,255,371 to Schosser et al. Thespecification of this patent, column 1, line 46 to column 3 line 4 isincorporated by reference into the present specification. Specificphosphinates mentioned include aluminum diethylphosphinate (DEPAL), andzinc diethylphosphinate (DEPZN). The phosphinates have the formulas (I)and (II):[(R¹)(R²)(PO)—O]_(m) ⁻M^(m+)  (I)and[(O—POR¹)(R³)(POR²—O)]²⁻ _(n)M^(m+) _(x),  (II),and include polymers comprising such formula I or II, wherein R¹ and R²are the same or different and are H, C₁-C₆ alkyl, linear or branched, orC₆-C₁₀ aryl; and R³ is C₁-C₁₀, alkylene, linear or branched, C₆-C₁₀arylene, C₇-C₁₁ alkylarylene, or C₇-C₁₁ arylalkylene; M is an alkalineearth metal, alkali metal, Al, Ti, Zn, Fe, or boron; m is 1, 2, 3 or 4;n is 1, 2, or 3; and x is 1 or 2. In an embodiment R¹ and R² are thesame and are C₁-C₆-alkyl, linear or branched, or phenyl; R³ isC₁-C₁₀-alkylene, linear or branched, C₆-C₁₀-arylene, -alkylarylene or-arylalkylene; M is magnesium, calcium, aluminum, zinc, or a combinationthereof; m is 1, 2 or 3; n is 1, 2 or 3; and x is 1 or 2. R¹ and R² canbe H, in addition to the substituents referred to set forth in thepatent. This results in a hypophosphite, a subset of phosphinate, suchas calcium hypophosphite, aluminum hypophosphite, and the like.

In a specific embodiment M is aluminum, and R¹ and R² are the same andare H, C₁-C₆ alkyl, linear or branched; and R³ is C₁-C₁₀ alkylene,linear or branched. A commercial example of a phosphinic acid saltincludes aluminum diethyl phosphinic acid (Al-DPA), commerciallyavailable from Clariant Corp.

The composition comprises from 5 to 15 wt %, specifically from 8 to 14wt %, even more specifically from 10 to 12.5 wt % of a flame retardantphosphinate salt, based on the total weight of the composition.

The thermoplastic polyester composition also comprises a reinforcingfiller, for example rigid fibers such as glass fibers, carbon fibers,metal fibers, ceramic fibers or whiskers, and the like. Glass fiberstypically have a modulus of greater than or equal to about 6,800megaPascals, and can be chopped or continuous. The glass fiber can havevarious cross-sections, for example, round, trapezoidal, rectangular,square, crescent, bilobal, trilobal, and hexagonal. Glass fibers can bein the form of chopped strands having an average length of from 0.1 mmto 10 mm, and having an average aspect ratio of 2 to 5. In articlesmolded from the compositions, shorter lengths will typically beencountered because during compounding considerable fragmentation canoccur.

In some applications it can be desirable to treat the surface of thefiber, in particular a glass fiber, with a chemical coupling agent toimprove adhesion to a thermoplastic resin in the composition. Examplesof useful coupling agents are alkoxy silanes and alkoxy zirconates.Amino, epoxy, amide, or thio functional alkoxy silanes are especiallyuseful. Fiber coatings with high thermal stability are preferred toprevent decomposition of the coating, which could result in foaming orgas generation during processing at the high melt temperatures requiredto form the compositions into molded parts.

The reinforcing filler, for example a glass fiber, is present in thecomposition in an amount from 25 to 35 wt %, specifically from 20 to 40%by weight, and most preferably, from 25 to 35% by weight.

In still other embodiments, the compositions can optionally additionallycomprise a particulate (non-fibrous) organic filler, which can impartadditional beneficial properties to the compositions such as thermalstability, increased density, stiffness, and/or texture. Exemplaryparticulate fillers are inorganic fillers such as alumina, amorphoussilica, alumino silicates, mica, clay, talc, glass flake, glassmicrospheres, metal oxides such as titanium dioxide, zinc sulfide,ground quartz, and the like.

In some embodiments, the reinforcing filler, for example glass fibers,is used in combination with a flat, plate-like filler, for example talc,mica or flaked glass. Typically, the flat, plate-like filler has alength and width at least ten times greater than its thickness, wherethe thickness is from 1 to about 1000 microns. Combinations of rigidfibrous fillers with flat, plate-like fillers can reduce warp of themolded article. A specific particulate filler is talc, in particular atalc filler having an average largest dimension of less than 0.9micrometers. In addition, or in the alternative, the filler can have amedian particle size of less than 0.9 micrometers. In an embodiment, theequivalent spherical diameter of the particle is used to determineparticle size. Use of these types of filler provides molded articleshaving both low shrinkage and a smooth surface finish. Use of thesetypes of filler can also aid the crystallization of the polyester, andincrease heat resistance of the composition. Such talcs are commerciallyavailable from Barretts Minerals Inc. under the trade name ULTRATALC®609.

When present, the particulate filler is used in an amount from more thanzero to 3 wt %, specifically more than 0 to 2 wt %, more specificallyfrom 0.1 to 1 wt %.

The composition further comprises a specific amount of a specificcombination of two types impact modifiers, a poly(ether-ester) elastomerand a (meth)acrylate impact modifier. It has surprising been found thatuse of only a single impact modifier, or a combination of impactmodifiers outside of the specified range, adversely affects the desiredcombination of properties. In a specific embodiment, no other impactmodifiers are present in the composition.

Poly(ester-ether) elastomers are copolymers that contain “hard blocks”(derived from the polyester units) and “soft blocks” (derived from thepolyether units) that provide the polymer with elastomeric properties.The copolymers can be characterized by the melting temperature (Tm) ofthe hard block and the glass transition temperature (Tg) of the softblock and. In general, the Tm of the hard block can be 120 to 200° C.,specifically 150 to 195° C., and the Tg of the soft block can be −25 to−85° C., specifically −45 to −65° C.

The poly(ester-ether) elastomers accordingly comprise units derived fromthe reaction of a dicarboxylic acid component (or chemical equivalentthereof) with two types of diols (or chemical equivalent thereof), ashort chain C₁₋₁₀ diol, and a long-chain poly(oxyalkylene)diol.

The dicarboxylic acid component can be one or more of the dicarboxylicacids described above in connection with the polyesters. In oneembodiment, the dicarboxylic acid is aromatic, for example terephthalicacid, isophthalic acid, or a combination comprising at least one of theforegoing acids. In a specific embodiment, the dicarboxylic acid isterephthalic acid. In another embodiment, the dicarboxylic acid is acombination of terephthalic acid and isophthalic acid.

Suitable short chain diols include C₁₋₈ diols as described above inconnection with the polyester. Specific diols are ethylene glycol andbutane diol, even more specifically butane diol.

The poly(oxyalkylene)diol is derived from the polymerization of a C₁₋₆diol or a combination comprising one or more C₁₋₆ diols, in particularC₂₋₄ diols, or the chemical equivalents thereof.Poly(oxytetramethylene)glycol is preferred, and can be prepared by wellknown techniques. The poly(oxyalkylene)diol, in particular thepoly(oxytetramethylene)glycol, has a weight average molecular weight(Mw) of 100 to 5,000, or more specifically, 150 to 4,000, or even morespecifically, 200 to 3,000.

The poly(ether-ester) elastomers can accordingly comprise long-chainester units of formula (III):-GOC(O)R′C(O)O—  (III);and short-chain ester units having units of formula (IV):-DOC(O)R′C(O)O—  (IV),wherein R′ is a divalent aromatic radical remaining after removal ofcarboxyl groups from terephthalic acid, isophthalic acid, or acombination of terephthalic acid and isophthalic acid; G is s divalentpolyalkylene oxide radical remaining after removal of terminal hydroxylgroups from a poly(alkylene oxide) glycol having a number-averagemolecular weight of 100 to 2500 Daltons; and D is the divalent alkyleneradical remaining after removal of hydroxyl groups from an aliphaticdiol having a molecular weight from 62 to 286.

A specific poly(ester-ether) elastomers is a poly(butyleneterephthalate/isophthalate-oxytetramethylene) copolymer, i.e., apoly(butylene terephthalate-polytetrahydrofuran) block copolymer. Thecopolymer comprises 25 to 65 wt %, more specifically 30 to 60 wt %, evenmore specifically 25 to 55 wt % of units derived frompoly(oxytetramethylene)glycol or chemical equivalents thereof, based onthe weight of the copolymer.

The poly(butylene terephthalate-oxytetramethylene) copolymer can furthercomprise isophthalic acid in addition to terephthalic acid. In oneembodiment, the poly(butyleneterephthalate/isophthalate-oxytetramethylene) copolymer comprises 0 to40 mole % of units derived from isophthalic acid or a chemicalequivalent thereof, based on the total number of isophthalate andterephthalate units. For example, the poly(butyleneterephthalate/isophthalate-oxytetramethylene) copolymer can compriseless than 5 mole % of isophthalate units, specifically 0 to 5 mole % ofisophthalate units, based on the total number of isophthalate andterephthalate units in the copolymer. In another embodiment, thepoly(butylene terephthalate/isophthalate-oxytetramethylene) copolymercomprises greater than 5 mole % of isophthalate units, specifically 5 to40 mole %, based on the total number of isophthalate and terephthalateunits in the copolymer.

A variety of poly(ether-ester) copolymers are commercially available,for example under the trademarks ARNITEL EM400 and ARNITEL EL630poly(ether-ester) copolymers from DSM; HYTREL 3078, HYTREL 4056, HYTREL4556, and HYTREL 6356 poly(ether-ester) copolymers from DuPont; andECDEL 9966 poly(ether-ester) copolymer from Eastman Chemical. In allcases, the soft block is derived from tetrahydrofuran. In the HYTREL4556, HYTREL 6356, ARNITEL EM400, and ARNITEL EL630 poly(ether-ester)copolymers, the hard block is based on poly(butylene terephthalate)(PBT). In the HYTREL 4056 poly(ether-ester) copolymer, the hard blockcontains isophthalate units in addition to terephthalate units. In theECDEL 9966 poly(ether-ester) copolymer, the hard block is based onpoly(1,4-cyclohexane-dimethanol-1,4-cyclohexane dicarboxylate) (PCCD)units. In another embodiment, the poly(ether-ester) elastomer caninclude a thermoplastic copolyetherester elastomer derived frompolyethylene terephthalate, in particular, post-consumer polyethyleneterephthalate. The random copolyetherester contains a modified, randompolybutylene terephthalate copolymer block that is derived from apolyethylene terephthalate component selected from the group consistingof polyethylene terephthalate and polyethylene terephthalate copolymers,or a combination thereof; and contains at least one residue derived fromthe polyethylene terephthalate component; and a polyalkylene oxidecopolymer block that is derived from a polyethylene terephthalatecomponent and polyalkylene oxide glycol, and contains polyalkylene oxideand at least one residue derived from the polyethylene terephthalatecomponent. Such random copolyetheresters are disclosed in U.S. Publ.2008/0027167, and is commercially available under the trademark VALOX iQelastomer, which can be available from SABIC Innovative Plastics.

The impact modifier component also comprises a (meth)acrylate impactmodifier. A (meth)acrylate impact modifier includes graft and/or coreshell structures having a rubbery component with a Tg below 0° C.,preferably between about −40° to about −80° C., and which include apoly(alkyl(meth)acrylate) or polyolefin grafted with a poly(methylmethacrylate) or styrene-acrylonitrile copolymer.

Typical core materials in core-shell impact modifiers consistsubstantially of a (meth)acrylate rubber, for example a (meth)acrylaterubber of derived from a C4-12 acrylate. Typically, one or more shellsare grafted on the core. Usually these shells are built up from a vinylaromatic compound, a vinyl cyanide, an alkyl(meth)acrylate,(meth)acrylic acid, or a combination thereof. The shell can be derivedfrom an alkyl(meth)acrylate, more specifically a methyl(meth)acrylate.The core and/or the shell(s) often comprise multi-functional compoundsthat can act as a cross-linking agent and/or as a grafting agent. In oneembodiment, the (meth)acrylate impact modifier has a crosslinkedpoly(butyl acrylate) core with a grafted poly(methyl methacrylate)shell.

Core-shell acrylic rubbers can be of various particle sizes, for examplefrom 300-800 nm, although larger particles, or mixtures of small andlarge particles, can also be used. In some instances, (meth)acrylateimpact modifier with a particle size of 350-450 nm is used. In otherapplications where higher impact is desired, particle sizes of 450-550nm or 650-750 nm can be used.

Specific (meth)acrylate impact modifiers include the core-shell polymersavailable from Rohm & Haas (now Dow Advanced Materials) under the tradename PARALOID®, including, for example, PARALOID® EXL3691 and PARALOID®EXL3330, EXL3300 and EXL2300.

Other (meth)acrylate impact modifiers include ethylene-acrylic acidcopolymers (EEA), sold by Dupont under the trade name ELVALOY;ethylene-methacrylate-glycidyl methacrylate copolymers (E-GMA-MA), soldby Arkema under the trade name LOTADER®; and polyethylene-g-glycidylmethacrylate (10%), sold by Sumitomo Chemical Co. under the trade nameIGETABOND E.

The impact modifier component is present in the composition in an amountfrom more than 0 to less than 5 wt %, specifically from 2 to 2.5 wt %.

In a specific embodiment, the impact modifier component comprises frommore than 0 to 5 wt %, specifically from 2 to 4 wt %, of a combinationof (i) a poly(butylene terephthalate-polytetrahydrofuran) blockcopolymer and (ii) a core-shell impact modifier having a crosslinkedpoly(butyl acrylate) core with a grafted poly(methyl methacrylate)shell.

The polyester compositions further comprise from more than 0 to 5 wt %,specifically from 0.5 to 5 wt % of an encapsulated particulatefluoropolymer, in particular poly(tetrafluoroethylene) encapsulated by astyrene-acrylonitrile copolymer). Small amounts of other fluoropolymerscan be used, for example those comprising units derived from fluorinatedmonomers such as 3,3,3-trifluoropropene, 3,3,3,4,4-pentafluoro-1-butene,hexafluoropropylene, vinyl fluoride; vinylidene fluoride,1,2-difluoroethylene, and the like, or a mixture comprising at least oneof the foregoing monomers

The fluoropolymer is encapsulated styrene-acrylonitrile (SAN). PTFEencapsulated in styrene-acrylonitrile is also known as TSAN.

Encapsulated fluoropolymers can be made by polymerizing theencapsulating polymer in the presence of the fluoropolymer, for examplean aqueous dispersion of the fluoropolymer. Alternatively, thefluoropolymer can be pre-blended with a second polymer, such as for,example, an aromatic polycarbonate or SAN to form an agglomeratedmaterial. Either method can be used to produce an encapsulatedfluoropolymer. The relative ratio of monovinyl aromatic monomer andmonovinylic comonomer in the rigid graft phase can vary widely dependingon the type of fluoropolymer, type of monovinylaromatic monomer(s), typeof comonomer(s), and the desired properties of the composition. Therigid phase can comprise 10 to 95 wt % of monovinyl aromatic monomer,specifically about 30 to about 90 wt %, more specifically 50 to 80 wt %monovinylaromatic monomer, with the balance of the rigid phase beingcomonomer(s). The SAN can comprise, for example, about 75 wt % styreneand about 25 wt % acrylonitrile based on the total weight of thecopolymer. An exemplary TSAN comprises about 50 wt % PTFE and about 50wt % SAN, based on the total weight of the encapsulated fluoropolymer.

The molding composition can optionally comprise a small amount of acharring polymer, in particular a polyetherimide (PEI). A commerciallyavailable polyetherimide is available from SABIC Innovative Plastics Co.under the trade name ULTEM® 1010. Other charring polymers include,poly(phenylene ether), poly(phenylenesulfide), polysulphones,polyethersulphones, poly(phenylenesulphide oxide) (PPSO), andpolyphenolics (e.g., novolacs). Use of a polyetherimide in compositionscomprising aluminum phosphinate salts can improve the mechanicalproperties of the compositions, in particular tensile strength andimpact properties. High temperature molding stability can also befurther improved, as well as melt stability.

The charring polymer, in particular PEI, can accordingly be present inan amount from 0 to less than 5 wt % of the composition, morespecifically from more than 0 to less than 3 wt %, by even morespecifically from more than 0 to less than 1 wt %, based on the totalweight of the composition.

However, in a unique advantage of the current compositions, improvementin flexural modulus, notched and unnotched Izod impact strength, tensilestress at break and/or elastic modulus, and high CTI is observed whenthe composition comprises no polyetherimide. Thus, in one embodiment, nopolyetherimide is present. In another embodiment, no charring polymer ispresent. In an embodiment wherein the composition contains nopolyetherimide, an article molded from the composition exhibits a CTI(Comparative Tracking Index) of 600 volts.

A stabilizer component is further present in the composition, in anamount from more than 0 to 2 wt %, specifically 0.01 to 1 wt %, evenmore specifically 0.05 to 0.5 wt %. As used herein, a “stabilizer” isinclusive of an antioxidant, thermal stabilizer, radiation stabilizer,ultraviolet light absorbing additive, and the like, and combinationsthereof. In one embodiment the stabilizer component comprises anantioxidant.

Exemplary antioxidants include organophosphites such as tris(nonylphenyl)phosphite, tris(2,4-di-t-butylphenyl)phosphite,bis(2,4-di-t-butylphenyl)pentaerythritol diphosphite, distearylpentaerythritol diphosphite; alkylated monophenols or polyphenols;alkylated reaction products of polyphenols with dienes, such astetrakis[methylene(3,5-di-tert-butyl-4-hydroxyhydrocinnamate)]methane;butylated reaction products of para-cresol or dicyclopentadiene;alkylated hydroquinones; hydroxylated thiodiphenyl ethers;alkylidene-bisphenols; benzyl compounds; esters ofbeta-(3,5-di-tert-butyl-4-hydroxyphenyl)-propionic acid with monohydricor polyhydric alcohols; esters ofbeta-(5-tert-butyl-4-hydroxy-3-methylphenyl)-propionic acid withmonohydric or polyhydric alcohols; esters of thioalkyl or thioarylcompounds such as distearylthiopropionate, dilaurylthiopropionate,ditridecylthiodipropionate,octadecyl-3-(3,5-di-tert-butyl-4-hydroxyphenyl)propionate,pentaerythrityl-tetrakis[3-(3,5-di-tert-butyl-4-hydroxyphenyl)propionate;amides of beta-(3,5-di-tert-butyl-4-hydroxyphenyl)-propionic acid, orcombinations comprising at least one of the foregoing antioxidants. Aspecific antioxidant is a hindered phenol stabilizer, pentaerythritoltetrakis(3,5-di-tert-butyl-4-hydroxyhydrocinnamate), sold under thetrade name IRGANOX® 1010 from Ciba Specialty Chemicals.

Exemplary heat stabilizer additives include organophosphites such astriphenyl phosphite, tris-(2,6-dimethylphenyl)phosphite, tris-(mixedmono- and di-nonylphenyl)phosphite; phosphonates such as dimethylbenzenephosphonate, phosphates such as trimethyl phosphate, or combinationscomprising at least one of the foregoing heat stabilizers. Heatstabilizers are used in amounts of 0.01 to 0.1 parts by weight, based on100 parts by weight of the total composition, excluding any filler.

Light stabilizers and/or ultraviolet light (UV) absorbing additives canalso be used. Exemplary light stabilizer additives includebenzotriazoles such as 2-(2-hydroxy-5-methylphenyl)benzotriazole,2-(2-hydroxy-5-tert-octylphenyl)-benzotriazole and 2-hydroxy-4-n-octoxybenzophenone, or combinations comprising at least one of the foregoinglight stabilizers. Light stabilizers are used in amounts of 0.01 to 5parts by weight, based on 100 parts by weight of the total composition,excluding any filler.

Exemplary UV absorbing additives include hydroxybenzophenones;hydroxybenzotriazoles; hydroxybenzotriazines; cyanoacrylates;oxanilides; benzoxazinones;2-(2H-benzotriazol-2-yl)-4-(1,1,3,3-tetramethylbutyl)-phenol (CYASORB®5411); 2-hydroxy-4-n-octyloxybenzophenone (CYASORB® 531);2-[4,6-bis(2,4-dimethylphenyl)-1,3,5-triazin-2-yl]-5-(octyloxy)-phenol(CYASORB® 1164); 2,2′-(1,4-phenylene)bis(4H-3,1-benzoxazin-4-one)(CYASORB® UV-3638);1,3-bis[(2-cyano-3,3-diphenylacryloyl)oxy]-2,2-bis[[(2-cyano-3,3-diphenylacryloyl)oxy]methyl]propane(UVINUL® 3030); 2,2′-(1,4-phenylene)bis(4H-3,1-benzoxazin-4-one);1,3-bis[(2-cyano-3,3-diphenylacryloyl)oxy]-2,2-bis[[(2-cyano-3,3-diphenylacryloyl)oxy]methyl]propane;nano-size inorganic materials such as titanium oxide, cerium oxide, andzinc oxide, all with particle size less than or equal to 100 nanometers;or combinations comprising at least one of the foregoing UV absorbers.UV absorbers are used in amounts of 0.01 to 5 parts by weight, based on100 parts by weight of the total composition, excluding any filler.

With the proviso that flame retardance properties and mechanicalproperties such as impact strength and flexural modulus are notsignificantly adversely affected, the compositions can further compriseother conventional additives used in polyester polymer compositions suchas mold release agents, plasticizers, quenchers, lubricants, antistaticagents, processing aids, dyes, pigments, laser marking additives, andthe like. A combination comprising one or more of the foregoing or otheradditives can be used. Plasticizers, lubricants, and/or mold releaseagents can be specifically mentioned. There is considerable overlapamong these types of materials, which include phthalic acid esters suchas dioctyl-4,5-epoxy-hexahydrophthalate;tris-(octoxycarbonylethyl)isocyanurate; tristearin; di- orpolyfunctional aromatic phosphates such as resorcinol tetraphenyldiphosphate (RDP), the bis(diphenyl)phosphate of hydroquinone and thebis(diphenyl)phosphate of bisphenol A; poly-alpha-olefins; epoxidizedsoybean oil; silicones, including silicone oils; esters, for example,fatty acid esters such as alkyl stearyl esters, e.g., methyl stearate,stearyl stearate, pentaerythritol tetrastearate, and the like;combinations of methyl stearate and hydrophilic and hydrophobic nonionicsurfactants comprising polyethylene glycol polymers, polypropyleneglycol polymers, poly(ethylene glycol-co-propylene glycol) copolymers,or a combination comprising at least one of the foregoing glycolpolymers, e.g., methyl stearate and polyethylene-polypropylene glycolcopolymer in a solvent; waxes such as beeswax, montan wax, and paraffinwax. Such materials are used in amounts of 0.1 to 1 parts by weight,based on 100 parts by weight of the total composition, excluding anyfiller. An exemplary mold release agent is pentaerythritoltetrastearate, available from Faci SpA.

The compositions can be prepared by blending the components of thecomposition, employing a number of procedures. In an exemplary process,the polyester component, reinforcing filler, melamine flame retardantsynergist, phosphinate salt flame retardant, impact modifier component,poly(tetrafluoroethylene) encapsulated by a styrene-acrylonitrilecopolymer, stabilizer, and optionally polyetherimide are placed into anextrusion compounder to produce molding pellets. The components aredispersed in a matrix in the process. In another procedure, thecomponents and reinforcing filler are mixed by dry blending, and thenfluxed on a mill and comminuted, or extruded and chopped. Thecomposition and any optional components can also be mixed and directlymolded, e.g., by injection or transfer molding techniques. Preferably,all of the components are freed from as much water as possible. Inaddition, compounding is carried out to ensure that the residence timein the machine is short; the temperature is carefully controlled; thefriction heat is utilized; and an intimate blend between the componentsis obtained.

The components can be pre-compounded, pelletized, and then molded.Pre-compounding can be carried out in conventional equipment. Forexample, after pre-drying the polyester composition (e.g., for fourhours at 120° C.), a single screw extruder can be fed with a dry blendof the ingredients, the screw employed having a long transition sectionto ensure proper melting. Alternatively, a twin screw extruder withintermeshing co-rotating screws can be fed with resin and additives atthe feed port and reinforcing additives (and other additives) can be feddownstream. In either case, a generally suitable melt temperature willbe 230° C. to 300° C. The pre-compounded composition can be extruded andcut up into molding compounds such as conventional granules, pellets,and the like by standard techniques. The composition can then be moldedin any equipment conventionally used for thermoplastic compositions,such as a Newbury or van Dorn type injection molding machine withconventional cylinder temperatures, at 230° C. to 280° C., andconventional mold temperatures at 55° C. to 95° C. The moldedcompositions provide an excellent balance of impact strength and flameretardancy.

In particular, the compositions provide excellent flame retardancy whenmolded into either thick or thin components. One set of test conditionscommonly accepted and used as a standard for flame retardancy is setforth in Underwriters Laboratories, Inc. Bulletin 94, which prescribescertain conditions by which materials are rated for self-extinguishingcharacteristics. Another set of conditions commonly accepted and used(especially in Europe) as a standard for flame retardancy is the GlowWire Ignition Test (GWIT), performed according to the Internationalstandard IEC 695-2-1/2. A 0.8 mm thick molded sample comprising thecomposition can have a UL-94 flammability rating of V0.

An article can be molded from the thermoplastic polyester composition asdescribed above. The article can include computer fans, electricalconnectors, automotive battery housings, and lighting sockets.

A molded article comprising the composition can have a flexural modulusof from 3000 MPa to 20000 MPa, more specifically more than 9800 MPa to20000 MPa, measured in accordance with ASTM D790, and the flexuralstress at break can be from 120 to 200 MPa, more specifically 130 to 190MPa, even more specifically more than 150 MPa to 190 MPa, measured inaccordance with ASTM D790.

A molded article comprising the composition can have good impactproperties, for example, an unnotched Izod impact strength from to 300to 700 J/m, more specifically, more than 470 J/m to 700 J/m, as measuredat 23° C. in accordance with ASTM D256.

In a specific embodiment, the glass-filled, chlorine- and bromine-freepoly(alkylene ester) flame retardant composition containing acombination of impact modifiers can have a combination of highly usefulphysical properties, namely, good flame retardance performance (e.g., arating of V0 at 0.80 mm), higher CTI performance, improved impactproperties and improved flexural properties, as compared to aglass-filled, chlorine and bromine-free poly(alkylene ester) flameretardant composition that contains polyimide but no elastomers. Morespecifically, the compositions containing a combination of elastomerscan meet targeted performance properties, namely: (a) a flexural modulusgreater than 9800 MPa, (b) a flexural stress greater than 150 MPa, (c)an unnotched impact strength greater than 470 Joules/meter, and (d) arating of V0 at a thickness of 0.8 mm, measured in accordance with theUL 94 protocol.

For example, an article molded from the following thermoplasticpolyester composition exhibits (a) a flexural modulus that is more than9800 MPa, (b) a flexural stress is more than 150 MPa, (c) an unnotchedimpact strength that is more than 470 Joules/meter, and (d) a V0 ratingat 0.8 mm, measured in accordance with UL 94, when the compositioncomprises, based on the weight of the composition, a combination of: (a)from 40 to 60 wt % of polybutylene terephthalate; (b) from 25 to 35 wt %glass fiber filler; (c) from 2 to 8 wt % of a flame retardant synergistselected from the group consisting of melamine polyphosphate, melaminecyanurate, melamine pyrophosphate, melamine phosphate, and combinationsthereof; (d) from more than 10 to 15 wt % a phosphinate of formula (I)described herein a diphosphinate of formula (II) described herein,and/or a polymer derived from the phosphinate of formula (I) or thediphosphinate of the formula (II), (e) at least 1 to less than 5 wt % ofimpact modifier component comprising a combination of (i) apoly(butylene terephthalate-polytetrahydrofuran) block copolymer and(ii) a core-shell (meth)acrylate impact modifier having a crosslinkedpoly(butyl acrylate) core with a grafted poly(methyl methacrylate)shell; (f) from more than 0 to 5 wt % poly(tetrafluoroethylene)encapsulated by a styrene-acrylonitrile copolymer; and (g) from morethan 0 wt % to 2 wt % of a stabilizer; wherein the halogen freecomposition contains less than 2 wt % of a polyetherimide.

Advantageously, it is now possible to make glass filled halogen freeflame retarding compositions that exhibit good flame retardancyperformance (i.e., V0 at 0.80 mm), higher CTI performance, improvedimpact properties and improved flexural properties. Our inventionprovides an eco-FR thermoplastic polyester composition having good flameretardant properties and comparable or improved mechanical properties,including ductility, flexural strength, CTI, and stiffness relative tocompositions comprising halogenated flame retardants and eco-FRcompositions comprising PEI.

It should be clear that the compositions and articles disclosed hereincan include reaction products of the above described components used informing the compositions and articles.

The invention is further illustrated by the following non-limitingexamples, in which all parts are by weight unless otherwise stated.

EXAMPLES

The following materials are used in Examples 1 to 7 (i.e., E1 to E7) andComparative Examples 1 to 25 (i.e., CE1 to CE25). Table 1 shows thenomenclature used as well as a description.

TABLE 1 Abbreviation, Description and Sources of Materials used inExamples Abbreviation Description Source VALOX 315 Intrinsic viscosity =1.19 dl/g, SABIC Innovative Mn = 110,000 g/mol Plastics Company VALOX195 Intrinsic viscosity = 0.66 dl/g, SABIC Innovative Mn = 53400 g/molPlastics Company Glass Fiber 13-micron diameter PPG Industries MPPMelamine polyphosphate Ciba Specialty Al-DPA Aluminum diethyl phosphinicClariant acid PEI Polyetherimide (ULTEM 1010) SABIC Innovative PlasticsCompany TSAN SAN encapsulated PTFE SABIC Innovative Plastics Company AOHindered phenol stabilizer Ciba Specialty PETS Pentaerythritoltetrastearate Faci SpA ULTRATALC Talc (avg particle size <0.90 Barrettsmicrometer) ELVALOY Ethylene-ethyl acrylate Dupont 2615 AC copolymerIGETABOND E Polyethylene-g-glycidyl Sumitomo methacrylate (10%) LOTADERE-GMA-MA Arkema HYTREL Poly(butylene tere/iso phthalate- Dupontco-polyoxybutylene) PARALOID Acrylic polymer impact modifier Rohm & HaasEXLTechniques and Procedures

Extrusion/Molding Procedures. The components as shown in Table 1 aretumble blended and then extruded on a 27-mm twin-screw extruder with avacuum vented mixing screw, at a barrel and die head temperature of 240°C.-265° C. and a screw speed of 300 rpm. The extrudate is cooled througha water bath before pelletizing. ASTM Izod and flexural bars areinjection molded on a van Dorn molding machine with a set temperature ofapproximately 240° C. to 265° C. The pellets are dried for 3 to 4 hoursat 120° C. in a forced air-circulating oven before injection molding.

Un-notched Izod Testing/Flexural Testing/Flame Testing. Un-notched Izodtesting is performed on 75 mm×12.5 mm×3.2 mm bars in accordance withASTM D256. Flexural properties are measured in accordance with ASTM D790on molded samples having a thickness of 3.2 mm. Flame testing per UL 94protocol is conducted on flame bars with 0.80 mm thickness after both23° C./48 hr and 70° C./168 hr aging conditions.

CTI Testing Procedures. CTI is used to measure the electrical breakdown(tracking) properties of the test material. In order to test for CTI, aspecimen (2.54 cm diameter disk or larger) is molded from the pelletsand placed on a support. Two electrodes, 4 mm apart, touch the specimensurface. A solution of 0.1% ammonium chloride electrolyte solution isintroduced via a syringe. One drop falls every 30 seconds on the surfacebetween the electrodes. The test proceeds by setting the electrodes to afixed applied voltage between 100 volts to 600 volts, and turning thesyringe pump on. The voltage that caused failure at 50 drops ofelectrolytes is selected as a measure of susceptibility of a material totracking. Interpolation is used if necessary to obtain this voltage.Performance Level Categories (PLC) are used to avoid excessive impliedprecision and bias. The relationship between tracking index voltage andPLC is shown in Table 2.

TABLE 2 Relationship between tracking index and PLC Tracking Index (V)PLC Rating 600 and Greater 0 400 through 599 1 250 through 399 2 175through 249 3 100 through 174 4 <100 5

Examples 1-7 Comparative Examples 1-2

The purpose of Examples 1-7 is to make a glass-filled, chlorine andbromine-free poly(alkylene) ester composition containing a combinationof elastomers and evaluate their performance with regard to thefollowing properties: (i) flame retardance performance (i.e., V0 at 0.80mm), (ii) CTI performance, (iii) impact properties and (iv) flexuralproperties. These compositions are evaluated to determine whether theycertain minimum targeted performance properties, namely: (a) a flexuralmodulus greater than 9800 MPa, (b) a flexural stress greater than 150MPa, (c) an unnotched impact strength greater than 470 Joules/meter, and(d) a rating of V0 at a thickness of 0.8 mm, measured in accordance withthe UL 94 protocol.

The purpose of Comparative Examples 1-2 is compare the performanceproperties of the compositions of Examples 1-7 with (i) a glass-filled,chlorine and bromine-free poly(alkylene ester) flame retardantcomposition that contained polyimide but no elastomers (ComparativeExample 1) and (ii) a glass-filled, chlorine and bromine-freepoly(alkylene ester) flame retardant composition that contained nopolyimide and no elastomers (Comparative Example 2).

TABLE 3 Formulation and physical properties of 30% glass-filled,chlorine- and bromine- free, flame retardant poly(alkylene ester)compositions (Examples 1 to 7) Targeted Item Description UnitPerformance E1 E2 E3 E4 E5 E6 E7 VALOX 315 % 24.83 24.83 24.58 24.5824.58 25.58 25.33 VALOX 195 % 24.83 24.83 24.58 24.58 24.58 25.58 25.33Glass Fiber % 30.00 30.00 30.00 30.00 30.00 30.00 30.00 MPP % 5.00 5.005.00 5.00 5.00 5.00 5.00 Al-DPA % 12.50 12.50 12.50 12.50 12.50 11.0011.00 TSAN % 0.50 0.50 0.50 0.50 0.50 0.50 0.50 AO % 0.15 0.15 0.15 0.150.15 0.15 0.15 PETS % 0.20 0.20 0.20 0.20 0.20 0.20 0.20 ULTRATALC % — —— — — — 0.50 PEI — — — — — — — HYTREL % 1.00 1.50 1.88 1.25 1.88 1.501.50 PARALOID EXL % 1.00 0.50 0.63 1.25 0.63 0.50 0.50 Total 100 100 100100 100 100 100 Test Description Unit E1 E2 E4 E5 E6 E7 E8 FlexuralModulus MPa >9800 9935 9955 10300 10500 10400 9990 9820 Flexural Stressat MPa >150 157 158 157 160 154 158 157 Break Izod Impact J/m >470 493505 518 499 474 476 568 strength, Un- Notched, 23° C. Flame Rating -0.80 V0 V0 V0 V0 V0 V0 V0 V0 UL 94, 23° C./48 mm hr Flame Rating - 0.80V0 V0 V0 V0 V0 V0 V0 V0 UL 94, 70° C./168 mm hr CTI (100) V 600 600 — —— 600 600 CTI PLC Rating 0 0 — — — 0 0

TABLE 4 Formulation and physical properties of glass-filled, chlorine-and bromine-free, flame retardant poly(alkylene ester) compositions(Comparative Examples 1 to 2) Targeted Item Description Unit PerformanceCE1 CE2 VALOX 315 % 25.83 25.83 VALOX 195 % 25.83 25.83 Glass Fiber %25.00 30.00 MPP % 5.00 5.00 Al-DPA % 12.50 12.50 TSAN % 0.50 0.50 AO %0.15 0.15 PETS % 0.20 0.20 ULTRATALC % — — PEI (ULTEM 1010) % 5.00 —HYTREL % — — PARALOID EXL % — — EEA % — — IGETABOND E % — — LOTADER % —— Total 100 100 Test Description Unit CE1 CE2 Flexural Modulus MPa >98009670 10100 Flexural Stress at Break MPa >150 160 150 Izod Impactstrength, J/m >470 432 410 Un-Notched Flame Rating - UL 94, 0.80 mm V0V0 V0 23° C./48 hr Flame Rating - UL 94, 0.80 mm V0 V0 V0 70° C./168 hrCTI (100) V 250 — CTI PLC Rating 2 —Discussion

The results shown in Tables 3 and 4 indicate that it is possible to makea glass-filled, chlorine- and bromine-free poly(alkylene ester) flameretardant composition containing a combination of elastomers with usefulproperties, namely, good flame retardance performance (i.e., a rating ofV0 at 0.80 mm), higher CTI performance, improved impact properties andimproved flexural properties, in comparison to a glass-filled, chlorineand bromine-free poly(alkylene ester) flame retardant composition thatcontains polyimide but no elastomers. More particularly, the results ofExamples 1-7 show that the inventive compositions meet the minimumtargeted performance properties, namely: (a) a flexural modulus greaterthan 9800 MPa, (b) a flexural stress greater than 150 MPa, (c) anunnotched impact strength greater than 470 Joules/meter, and (d) arating of V0 at a thickness of 0.8 mm, measured in accordance with theUL 94 protocol. The compositions of Comparative Examples 1-2 do not meetthese properties.

It can be seen that in Examples E1 to E7 in Table 3, when no ULTEM 1010is present in the formulations and glass fiber content is 30%, theaddition of combinations of elastomers (HYTREL and PARALOID EXL) at a 2wt % level (E1 (1% HYTREL and 1% PARALOID EXL) and E2, E6, and E7 (1.5%HYTREL and 0.5% PARALOID EXL)) and a 2.5 wt % level (E3 and E5 (1.88%HYTREL and 0.63% PARALOID EXL)) and (E4 (1.25% HYTREL and 1.25% PARALOIDEXL)) can improve mechanical properties such as unnotched Izod impactstrength by at least 8.8%, while maintaining flame retardanceperformance (V0 at 0.8 mm) per UL 94, compared with CE1. Furthermore,the CTIs of E1, E2, E6, and E7 are also in much higher voltages thanCE1: 600 V for E1, E2, E6, and E7 as compared to 250 V for CE1. This isequivalent to a 2 PLC rating increase. Furthermore, when less Al-DPA isused in E6 and E7 (11%) as compared with in CE1 (12.5%), a UL 94 V0rating at 0.80 mm is still achieved. Especially in E7, where 0.5%ULTRATALC is present in the formulation, the unnotched impact strength(568 J/m) is largely improved from the 438 J/m observed for CE1, as wellas the 476 J/m of E6.

As shown in the comparative examples (Table 4), CE1 is a 25 wt % glassand 5 wt % polyimide (ULTEM 1010)-filled, chlorine- and bromine-freepoly(alkylene ester) flame retardant composition. CE2 is a 30 wt %glass-filled, chlorine- and bromine-free poly(alkylene ester) flameretardant composition with no polyimide (ULTEM 1010). When the 5 wt %ULTEM 1010 in CE1 is replaced with 5 wt % glass in CE2, the unnotchedIzod impact strength of the formulation drops by 5% (from 432 to 410J/m), even though the same V0 rating is achieved. The low impactstrength of CE2 limits its use in applications such as electricalconnectors and computer fans.

Comparative Examples 3-25

The purpose of Comparative Examples 3-25 is to compare the performanceof compositions containing a single elastomer with compositions having acombination of elastomers, as well as the performance of compositionscontaining a combination of elastomers in amounts outside the inventiveranges.

Examples are prepared and tested as described above. The results forComparative Examples CE3-CE25 are shown in Tables 5, 6, and 7.

TABLE 5 Formulation and physical properties of glass-filled, chlorine-and bromine-free, flame retardant poly(alkylene ester) compositions(Comparative Example 3 to 12) Targeted Item Description Unit PerformanceCE3 CE4 CE5 CE6 CE7 CE8 CE9 CE12 VALOX 315 % 23.33 23.33 23.33 23.3323.33 23.33 23.33 23.83 VALOX 195 % 23.33 23.33 23.33 23.33 23.33 23.3323.33 23.83 Glass Fiber % 30.00 30.00 30.00 30.00 30.00 30.00 30.0030.00 MPP % 5.00 5.00 5.00 5.00 5.00 5.00 5.00 5.00 Al-DPA % 12.50 12.5012.50 12.50 12.50 12.50 12.50 11.00 TSAN % 0.50 0.50 0.50 0.50 0.50 0.500.50 0.50 AO % 0.15 0.15 0.15 0.15 0.15 0.15 0.15 0.15 PETS % 0.20 0.200.20 0.20 0.20 0.20 0.20 0.20 ULTRATALC % — — — — — — — 0.50 PEI (ULTEM% — — — — — — — — 1010) HYTREL % 5.00 — — — — 2.50 3.75 — PARALOID % —5.00 — — — 2.50 1.25 1.25 EXL EEA % — — 5.00 — — — — — IGETABOND E % — —— 5.00 — — — — LOTADER % — — — — 5.00 — — — 100 100 100 100 100 100 100100 Test Description Unit CE3 CE4 CE5 CE6 CE7 CE8 CE9 CE12 FlexuralModulus MPa >9800 8570 9420 8820 8610 8370 9840 9700 9410 FlexuralStress at MPa >150 119 137 126 143 138 147 144 147 Break Izod ImpactJ/m >470 442 398 412 461 452 464 482 494 strength, Un- Notched, 23° C.Flame Rating - 0.80 V0 V0 V0 V0 V0 V0 V0 V0 V0 UL 94, 23° C./48 mm hrFlame Rating - 0.80 V0 V0 V0 V0 V1 V1 V0 V0 V2 UL 94, 70° C./168 mm hrCTI (100) V — — — — — — — — CTI PLC Rating — — — — — — — —

TABLE 6 Formulation and physical properties of glass-filled, chlorine-and bromine- free, flame retardant poly(alkylene ester) compositions(Comparative Example 13 to 19) Targeted Item Description UnitPerformance CE13 CE14 CE15 CE16 CE17 CE18 CE19 VALOX 315 % 24.58 24.5824.58 24.58 24.58 24.58 25.08 VALOX 195 % 24.58 24.58 24.58 24.58 24.5824.58 25.08 Glass Fiber % 30.00 30.00 30.00 30.00 30.00 30.00 30.00 MPP% 5.00 5.00 5.00 5.00 5.00 5.00 5.00 Al-DPA % 12.50 12.50 12.50 12.5012.50 12.50 11.00 TSAN % 0.50 0.50 0.50 0.50 0.50 0.50 0.50 AO % 0.150.15 0.15 0.15 0.15 0.15 0.15 PETS % 0.20 0.20 0.20 0.20 0.20 0.20 0.20ULTRATALC % — — — — — — 0.50 PEI (ULTEM % — — — — — — — 1010) HYTREL %2.50 — — — — 1.25 1.88 PARALOID % — 2.50 — — — 1.25 0.63 EXL EEA % — —2.50 — — — — IGETABOND E % — — — 2.50 — — — LOTADER % — — — — 2.50 — —100 100 100 100 100 100 100 Test Description Unit CE13 CE14 CE15 CE16CE17 CE18 CE19 Flexural Modulus MPa >9800 6460 9600 9250 9370 9190 106009860 Flexural Stress at MPa >150 110 141 133 148 147 150 155 Break IzodImpact J/m >470 420 442 371 471 470 447 506 strength, Un- Notched FlameRating - 0.80 V0 V0 V0 V0 V0 V1 V0 V0 UL 94, 23° C./48 mm hr FlameRating - 0.80 V0 V0 V0 V0 V1 V1 V0 V2 UL 94, 70° C./168 mm hr CTI (100)V — — — — — — — CTI PLC Rating — — — — — — —

TABLE 7 Formulation and physical properties of glass-filled, chlorine-and bromine-free, flame retardant poly(alkylene ester) compositions(Comparative Example 20 to 25) Targeted Item Description Unit PropertiesCE20 CE21 CE22 CE23 CE24 CE25 VALOX 315 % 24.83 24.83 25.83 25.58 25.2025.20 VALOX 195 % 24.83 24.83 25.83 25.58 25.20 25.20 Glass Fiber %30.00 30.00 30.00 30.00 30.00 30.00 MPP % 5.00 5.00 5.00 5.00 5.00 5.00Al-DPA % 12.50 12.50 10.50 10.50 12.50 12.50 TSAN % 0.50 0.50 0.50 0.500.50 0.50 AO % 0.15 0.15 0.15 0.15 0.15 0.15 PETS % 0.20 0.20 0.20 0.200.20 0.20 ULTRATALC % — — — 0.50 — — PEI (ULTEM 1010) % — — — — — —HYTREL % 2.00 — 1.50 1.50 1.25 — PARALOID EXL % — 2.00 0.50 0.50 1.25EEA % — — — — — — IGETABOND E % — — — — — — LOTADER % — — — — — — 100100 100 100 100 100 Test Description Unit CE20 CE21 CE22 CE23 CE24 CE25Flexural Modulus MPa >9800 9530 9760 10100 10200 8950 10200 FlexuralStress at Break MPa >150 153 156 161 164 143 154 Izod impact strength,J/m >470 531 417 508 561 429 466 Unnotched Flame Rating, UL 94, 0.80 mmV0 V0 V0 V0 V0 V0 V0 23° C./48 hr Flame Rating, UL 94, 0.80 mm V0 V2 V1V1 V0 V0 V0 70° C./168 hr CTI (100) V — — 600 550 — — CTI PLC Rating — —0 1 — —Discussion

The results shown in Tables 5, 6, and 7 (Comparative Examples 3-25)illustrate that use of a single elastomer, or two elastomers outside ofa relatively narrow range does not meet the minimum targeted performanceproperties; namely these compositions do not exhibit the followingcombination of properties: (a) a flexural modulus greater than 9800 MPa,(b) a flexural stress greater than 150 MPa, (c) an unnotched impactstrength greater than 470 Joules/meter, and (d) a rating of V0 at athickness of 0.8 mm, measured in accordance with the UL 94 protocol. Thecompositions of Comparative Examples 1-2 do not meet these properties.

As shown in Table 5, when impact modifiers including ELVALOY, IGETABOND,LOTADER, HYTREL, and PARALOID EXL are used individually at a level of 5wt %, the 30 wt % glass-filled, chlorine- and bromine-free poly(alkyleneester) flame retardant formulations (CE3 to CE7) show some disadvantagessuch as in low flexural modulus, low flexural stress at break, and lowunnotched Izod impact strength. In CE6 and CE7, flame retardanceperformance is rated as V1. In CE8 to CE9 and CE12, where the additionof combinations of elastomers (HYTREL Elastomer and PARALOID EXL) at alevel of 5 wt % is used, flexural stress at break is still lessdesirable, i.e., less than 150 MPa. In CE12, where 11% Al-DPA is used,the UL 94 rating at 0.80 mm is V1.

As shown in Table 6, when impact modifiers including ELVALOY, IGETABOND,LOTADER, HYTREL and PARALOID EXL are used individually at a level of 2.5wt %, the 30% glass-filled, chlorine- and bromine-free poly(alkyleneester) formulations (CE13 to CE17) show some disadvantages such as inlow flexural modulus, low flexural stress at break, and in some cases,low un-notched Izod impact strength. In CE16 and CE17, flame retardanceperformance is rated as V1. In CE18, where the addition of combinationsof elastomers (1.25% HYTREL and 1.25% PARALOID EXL) at a level of 2.5 wt% is used, flexural stress at break is still less desirable, i.e., lessthan 150 MPa. In CE19, where 11% Al-DPA is used, the UL 94 rating at0.80 mm is V2.

As shown in Table 7, when impact modifiers including HYTREL and PARALOIDEXL are used individually at a level of 2.0 wt %, the 30% glass-filled,chlorine- and bromine-free poly(alkylene ester) formulations (CE20 andCE21) show some disadvantages such as in low flexural modulus andfailure to meet V0 flame retardance at 0.80 mm. When impact modifiersincluding HYTREL and PARALOID EXL are used individually at a level of1.25 wt %, the 30% glass-filled, chlorine- and bromine-freepoly(alkylene ester) flame retardant formulations (CE24 and CE25) showsome disadvantages such as low flexural modulus (CE24) and low unnotchedIzod impact strength, i.e., less than 470 J/m. In CE22 to CE23,containing 2 wt % of a combination of elastomers (1.50% HYTREL and 0.5%PARALOID EXL) and 10.5 wt % of Al-DPA, the formulations show eitherinsufficient UL 94 rating (CE22) or less desirable CTI voltage, i.e.,less than 600V (CE23).

All patents and applications cited herein are incorporated byreferences. While the invention has been described with reference to apreferred embodiment, it will be understood by those skilled in the artthat various changes can be made and equivalents can be substituted forelements thereof without departing from the scope of the invention. Inaddition, many modifications can be made to adapt a particular situationor material to the teachings of the invention without departing fromessential scope thereof. Therefore, it is intended that the inventionnot be limited to the particular embodiment disclosed as the best modecontemplated for carrying out this invention, but that the inventionwill include all embodiments falling within the scope of the appendedclaims.

What is claimed is:
 1. A thermoplastic polyester composition comprising,based on the weight of the composition, a chlorine- and bromine-freecombination of: (a) from 40 to 60 wt % of poly(butylene terephthalate);(b) from 25 to 35 wt % of a glass fiber filler; (c) from 2 to 8 wt % ofa flame retardant synergist selected from the group consisting ofmelamine polyphosphate, melamine cyanurate, melamine pyrophosphate,melamine phosphate, and combinations thereof; (d) from more than 10 to15 wt % a phosphinate of formula (I)[(R¹)(R²)(PO)—O]⁻ _(m)M^(m+)  (I), a diphosphinate of formula (II)[(O—POR¹)(R³)(POR²—O)]²⁻ _(n)M^(m+) _(x)  (II), and/or a polymer derivedfrom the phosphinate of formula (I) or the diphosphinate of the formula(II), wherein R¹ and R² are identical or different and are H, linear orbranched C₁-C₆ alkyl, or C₆-C₁₀ aryl; R³ is C₁-C₁₀, linear or branchedalkylene, C₆-C₁₀ arylene, C₇-C₁₁ alkylarylene, or C₇-C₁₁ arylalkylene; Mis an alkaline earth metal, alkali metal, Al, Ti, Zn, Fe, or B; m is 1,2, 3 or 4; n is 1, 2, or 3; and x is 1 or 2; (e) at least 1% to lessthan 5 weight % of impact modifier component comprising a combination of(i) a poly(ether-ester) elastomer and (ii) a core-shell (meth)acrylateimpact modifier; wherein the poly(ether-ester) elastomer compriseslong-chain ester units of formula (III):-GOCOR′COO—  (III); and short-chain ester units having units of formula(IV):-DOCOR′COO—  (IV), wherein R′ is a divalent aromatic radical remainingafter removal of carboxyl groups from terephthalic acid, isophthalicacid, or a combination of terephthalic acid and isophthalic acid; G is adivalent polyalkylene oxide radical remaining after removal of terminalhydroxyl groups from a poly(alkylene oxide) glycol having anumber-average molecular weight of 100 to 2500; and D is a divalentalkylene radical remaining after removal of hydroxyl groups fromaliphatic diols having a molecular weight from 62 to 286; and whereinthe core-shell meth(acrylate) impact modifier has a crosslinkedpoly(butyl acrylate) core with a grafted poly(methyl methacrylate)shell; (f) from more than 0 to 5 wt % poly(tetrafluoroethylene)encapsulated by a styrene-acrylonitrile copolymer; and (g) from morethan 0 wt % to 2 wt % of a stabilizer; wherein the thermoplasticpolyester composition contains 0 to less than 3 wt % of apolyetherimide; and wherein an article molded from the compositionexhibits (a) a flexural modulus that is more than 9800 to less than orequal to 20000 MPa, measured in accordance with ASTM D790, (b) aflexural stress that is more than 150 to less than or equal to 190 MPa,measured in accordance with ASTM D790, (c) an unnotched impact strengththat is more than 470 to less than or equal to 700 Joules/meter,measured at 23° C. in accordance with ASTM D256, and (d) a V0 rating at0.8 mm, measured in accordance with UL
 94. 2. An article comprising thethermoplastic polyester composition of claim
 1. 3. The article of claim2, wherein the article is selected from the group consisting of computerfans, electrical connectors, automotive battery housings, and lightingsockets.
 4. The thermoplastic polyester composition of claim 1, whereinthe poly(ether-ester) elastomer is a poly(butyleneterephthalate-polytetrahydrofuran) block copolymer.
 5. The thermoplasticpolyester composition of claim 1, wherein the phosphorus flame retardantis present in an amount ranging from 11 to 12.5 wt %.
 6. Thethermoplastic polyester composition of claim 1, wherein the impactmodifier is present in an amount ranging from 2 to 2.5 wt %.
 7. Thethermoplastic polyester composition of claim 1, wherein the compositioncontains no polyetherimide, and an article extruded from the compositionexhibits a CTI (Comparative Tracking Index) of 600 volts.
 8. Thethermoplastic polyester composition of claim 1, wherein the flameretardant comprises the phosphinate of formula (I).
 9. The thermoplasticpolyester composition of claim 1, wherein the thermoplastic polyestercomposition contains less than 1 wt % of a polyetherimide.
 10. Thethermoplastic polyester composition of claim 1, wherein the impactmodifier component comprises from 2 to 4 wt % of a combination of apoly(butylene terephthalate-polytetrahydrofuran) block copolymer and acore-shell (meth)acrylate impact modifier having a crosslinkedpoly(butyl acrylate) core with a grafted poly(methyl methacrylate)shell.
 11. A thermoplastic polyester composition comprising, based onthe weight of the composition, a halogen-free combination of: (a) from40 to 60 wt % of poly(butylene terephthalate); (b) from 25 to 35 wt %glass fiber filler; (c) from 2 to 8 wt % of a flame retardant synergistselected from the group consisting of melamine polyphosphate, melaminecyanurate, melamine pyrophosphate, melamine phosphate, and combinationsthereof; (d) from more than 10 to 15 wt % a phosphinate of formula (I)[(R¹)(R²)(PO)—O]⁻ _(m)M^(m+)  (I), a diphosphinate of formula (II)[(O—POR¹)(R³)(POR²—O)]²⁻ _(n)M^(m+) _(x)  (II), and/or a polymer derivedfrom the phosphinate of formula (I) or the diphosphinate of the formula(II), wherein R′ and R² are identical or different and are H, or linearor branched C₁-C₆ alkyl; R³ is C₁-C₁₀, linear or branched alkylene; M isaluminum; m is 3; n is 3; and x is 1 or 2; (e) at least 1 to less than 5wt % of impact modifier component comprising a combination of (i) apoly(butylene terephthalate-polytetrahydrofuran) block copolymer and(ii) a core-shell (meth)acrylate impact modifier having a crosslinkedpoly(butyl acrylate) core with a grafted poly(methyl methacrylate)shell; (f) from more than 0 to 5 wt % poly(tetrafluoroethylene)encapsulated by a styrene-acrylonitrile copolymer; and (g) from morethan 0 wt % to 2 wt % of a stabilizer; wherein the thermoplasticpolyester composition contains 0 to less than 2 wt % of apolyetherimide; and wherein an article molded from the compositionexhibits (a) a flexural modulus that is more than 9800 to less than orequal to 20000 MPa, measured in accordance with ASTM D790, (b) aflexural stress is more than 150 to less than or equal to 190 MPa,measured in accordance with ASTM D790, (c) an unnotched impact strengththat is more than 470 to less than or equal to 700 Joules/meter,measured at 23° C. in accordance with ASTM D256, and (d) a V0 rating at0.8 mm, measured in accordance with UL
 94. 12. An article comprising thecomposition of claim
 11. 13. The article of claim 12, wherein thearticle is selected from the group consisting of computer fans,electrical connectors, automotive battery housings, and lightingsockets.